1. Field of the Invention
The present invention relates to a pattern transfer apparatus and a pattern forming method, and more particularly to a pattern transfer apparatus and a pattern forming method whereby a pattern is transferred onto a substrate by applying a mold on which the pattern has been formed onto a surface of the substrate on which liquid has been applied, curing the liquid, and then removing the mold.
2. Description of the Related Art
Photo nanoimprint lithography is known as a method of forming patterns in a manufacturing process which requires high-resolution processing, such as semiconductor device fabrication. In the photo nanoimprint lithography, a mold having topological patterns is pressed onto a surface of a substrate on which a resist layer has been applied, whereupon the resist layer is cured by light and the mold is then removed, thereby transferring the topological patterns to the resist layer on the surface of the substrate.
Japanese Patent Application Publication No. 2007-313439 discloses a resin application apparatus which includes: an inkjet device having actuators adapted to be controlled so as to intermittently eject droplets of resin liquid from a plurality of nozzle holes arranged in an array to deposit the droplets of resin liquid onto a surface of a substrate; and a linear or rotational drive device adapted to move the inkjet device and the substrate relatively at least in a direction perpendicular to the array of the nozzle holes or in a rotational direction. In order to form an extremely thin film of the resin (resist layer) of uniform thickness on the substrate surface, the resin liquid droplets are deposited on the substrate surface by the inkjet device, and then the liquid resin droplets are caused to spread on the substrate surface by spin coating.
Japanese Patent Application Publication No. 2007-516862 discloses an imprint method in which, in order to avoid trapping of gas (bubbles) in an imprint layer once patterned surface is formed, a mold is positioned so that the mold surface forms an oblique angle with respect to the substrate surface on which the imprint layer has been applied, referred to as cantilevering impingement. The mold is rotated so that all of droplets of the imprint material spread to become included in continuous sheet.
Japanese Patent Application Publication No. 2008-230027 discloses an imprint device in which a fluid is discharged toward a rear surface of a stamper opposing to the surface on which a micropattern is created or a rear surface of a material to be transferred opposing to the surface which comes into contact with the stamper so as to bend the stamper or the material to be transferred, in order to obtain an imprinted structure having a thin uniform pattern forming layer on the material to be transferred, by flattening waviness on a nanometer scale present on the surface of the material to be transferred, and reducing an unobstructed flow of a resin due to a locally loaded pressure on the material to be transferred and/or the stamper.
However, in the related art described above, when applying the liquid onto the substrate, there are problems of the following kinds in preventing non-uniformity in the film thickness and achieving uniform film thickness. For example, in the method described in Japanese Patent Application Publication No. 2007-313439, there are problems in that although uniform film thickness is achieved, costs increase due to the inclusion of additional steps, such as spin coating, and furthermore the method cannot be used when the liquid should be partially applied, to a portion to be imprinted, because the liquid is made to spread over the whole of the substrate surface ultimately by spin coating. Moreover, although Japanese Patent Application Publication No. 2007-516862 discloses that the mold is obliquely positioned to the substrate and rotated, it is silent about the deposition pattern in the liquid deposition by the inkjet in order to prevent non-uniformity in the film thickness. Furthermore, although Japanese Patent Application Publication No. 2008-230027 discloses that the stamper or the material to be transferred is bent and pressed so as to obtain the thin uniform pattern forming layer on the material to be transferred, it is also silent about prevention of non-uniformity in the film thickness when applying the resin layer onto the substrate.
When applying an imprint material onto a substrate, it is beneficial to use an inkjet head having a plurality of nozzles to eject liquid droplets of the material in order to improve productivity; however, if a plurality of nozzles are used, then the liquid ejection volume can vary with each nozzle, and if the liquid ejection is performed without any adjustment, the variations in the liquid ejection volume cause non-uniformity in the film thickness of the material during the imprint process. In the related art, there have been virtually no improvements of the deposition pattern when depositing the liquid of the imprint material to the substrate by the inkjet method.